Glaciation 5th year Geography Ms Carr

Learning Intention Visualise what glaciation is. Name and briefly explain the formation of glacial landforms. Recognise the landforms on a diagram, OS map and Aerial photograph.

Glaciation  Earth once covered with glaciers  Last glaciation ended around 10,000 years ago  Current interglacial period – Holocene  Two major glaciations have affected Ireland: i.The Munsterian, 300,000 to 132,000 years ago ii.The Midlandian, 79,000 to 13,000 years ago

Glaciers  Rivers of ice that move slowly.  Move downslope under the influence of gravity and the pressure of own weight.  Form where rate of accumulation of snow and ice is greater than rate of melting.  Largest reservoir of fresh water on Earth.

Types of Glaciers 1.Valley glaciers: form in mountainous locations and move down valleys. 2.Continental ice sheets/glaciers: enormous areas of glacial ice and snow.

Causes of an Ice Age  Change in the Earth’s orbit around the sun  Change in the angle of the Earth’s axis Chapter 13: Glacial Processes, Patterns & Associated Landforms

Processes of Glacial Erosion Glaciers erode the landscape they travel over in two ways: 1.Plucking 2.Abrasion Textbook page 146

Plucking Most effective where:  Rock is well jointed  Rock has already been weakened by freeze-thaw action  Bottom of glaciers scrape along valley floors – creates friction causing melting around the base of the glacier  Meltwater refreezes  Freezes around the rocks on the valley floor and these become part of the glacier  Glacier advances  Newly trapped rock is plucked out of the valley floor  New material is then used in process of abrasion

Abrasion  Occurs when the bedrock beneath the glacier is eroded by the debris/material embedded in the sides and bottom of the glacier  ‘Sandpaper effect’ – scrapes the rock over which it is travelling and leaves scratches or grooves in the rock  Striations – show the direction of the ice flow

Processes of Glacial Transportation 1.Basal sliding  Friction between the base of the glacier and the valley floor  Meltwater acts as a lubricant  Glacier slides downslope under the influence of gravity 2.Internal flow  Ice crystals react to pressure and gravity  Melting and refreezing  Ice changes internally over time without completely melting or breaking  Material transported by the glacier is called moraine.

Chapter 13: Glacial Processes, Patterns & Associated Landforms Factors affecting the rate of glacial erosion  Thickness of ice  Topography  Geology  Gradient  Accumulation and ablation

Landforms of Glacial Erosion Cirque / Corrie Arete Pyramidal Peak U-Shaped Valley Ribbon Lake Fjords

Landforms of Glacial Erosion 1.Cirque  Birthplace of a glacier  Depression in a mountain  Three steep sides  Also called a corrie or coom 2.Arête  Narrow ridge  Formed when two cirques formed side-by-side or back-to-back

Pyramidal Peak Formed when three or more cirques are eroded back-to-back or side-to-side around the sides of a mountain. Isolated peak in the centre.

Chapter 13: Glacial Processes, Patterns & Associated Landforms  Glaciers take the easiest route as they move from upland areas down through their valleys  Route is often a pre-existing V-shaped river valley  Glacier moves through this valley, changing the shape from a V-shape to a U-shape  Erode vertically and laterally  Valleys have steep sides and flat floors  Glacier cuts off interlocking spurs of the V-shaped valley leaving truncated spurs U-Shaped Valley

Ribbon Lakes Long, narrow lakes found in glaciated U-shaped valleys As a glacier advances through its valley it abrades the landscape Soft rock is abraded faster and easier than the harder resistant rock forming basins Within the rock basin meltwater and rainwater accumulates forming a ribbon lake Fjords Drowned U-shaped valleys Result of melting glaciers

OS Map Textbook page 149

Pairwork Quick Questions Name two processes of glacial erosion. What is the name given to material that is transported by the glacier? Name the landform that is said to be the birthplace of a glacier. How is an arete formed? Explain the formation of a ribbon lake.

Homework Textbook page 159 Questions 1-4

Landforms of Glacial Deposition Moraines Drumlins Erratics

Glacial Deposition  Dropping or laying down of sediment that was once transported by a glacier  Lowland areas  Deposited material is called glacial drift  Material deposited directly by ice is called till or boulder clay  Material deposited by glacial meltwater is known as fluvio-glacial deposits

Chapter 13: Glacial Processes, Patterns & Associated Landforms Examples of landforms of fluvio-glacial deposition  Eskers  Outwash plains  Kames and kettle holes

Moraine  Deposited debris  Various sizes ranging from large boulders to fine rock flour  Material may be angular or rounded in shape

Chapter 13: Glacial Processes, Patterns & Associated Landforms Five types of moraine i.Lateral moraine ii.Medial moraine iii.End/terminal moraine iv.Ground moraine v.Englacial moraine

Drumlins  Oval-shaped hills consisting of boulder clay  Show direction of glacier movement  Occur in swarms or cluster  ‘Basket of eggs’ topography  ‘Drowned drumlins’ – as the ice melted sea levels rose and the drumlins appear as islands in the sea

OS Map Textbook page 155

Erratics  Material transported by the glacier and are said to be ‘out of place’ when deposited  Provide information about the direction of the glacier and how far it has travelled – crag and tail  Esker – long winding ridges of stratified sand and gravel that wind its way across lowland areas

Chapter 13: Glacial Processes, Patterns & Associated Landforms Examples of landforms of fluvio-glacial deposition  Eskers  Outwash plains  Kames and kettle holes

Eskers Long winding ridges of stratified sand and gravel.

Outwash Plains  Glaciers melt  Release vast amounts of water  Spreads outwards beyond the end/terminal moraine  Carries large volumes of rock and gravels and sands

Kames  Piles of sediment consisting of gravels and sand  Deposited along the front of a retreating glacier

Kettle Holes  Blocks of ice separate from the main glacier  Buried partly in meltwater sediments  Blocks of ice melt leaving depressions or holes  Fill with water – form kettle hole lakes

LandformProcesses involved Description1 other factExample

Homework Textbook page 160 Questions

Exam Questions Long Q’s;Choice between fluvial / coastal / mass movement / glacial... Long Q’s; OS Map / Aerial Photograph Short Q’s; Variety of questions on glacial landforms.

Exam Questions